Many communication systems in development today deliver information between users in a purely digital format. It is often desirable that users within such systems be able to communicate with users within an external public switched telephone network (PSTN). Such communication can be difficult because digital communication systems typically utilize unique system-native digital signal formats to transfer information within the system. These signal formats are usually incompatible with the formats used by the PSTN and therefore conversions must be performed at the interface between the digital system and the PSTN.
Digital communication systems and PSTNs are each typically capable of carrying both voice and data signals. Digital systems generally use a vocoding algorithm to compress digital speech signals within the system and some form of protection protocol to protect the integrity of data within the system. PSTNs, on the other hand, generally use basic pulse code modulation (PCM) techniques to format speech signals being delivered within the network and some form of modem standard to deliver data within the PSTN.
As can be appreciated, to provide interoperation between a digital system and a PSTN, voice and data signals traversing the system interface must be appropriately converted. Traditionally, this has required a priori knowledge of signal type at the system interface to accurately convert the signals. Relatively complex signaling schemes (e.g., multi-numbering schemes) have been developed for providing this information at the interface to support the signal conversion process. These signaling schemes are usually very inefficient and utilize system resources that could otherwise be used for other purposes.
Therefore, there is a need for a method and apparatus that is capable of providing efficient interoperation between a digital communication system and a PSTN. It is desirable that the method and apparatus provide interoperation for both voice and data signals traversing the interface between the systems in a relatively seamless fashion. In addition, it is desirable that the method and apparatus provide such interoperation without the need for a priori knowledge of signal type at the interface.